In a dynamic rigid disk storage device, a rotating disk is employed to store information. Rigid disk storage devices typically include a frame to provide attachment points and orientation for other components, and a spindle motor mounted to the frame for rotating the disk. A read/write head is formed on a "head slider" for writing and reading data to and from the disk surface. The head slider is supported and properly oriented in relationship to the disk by a head suspension that provides both the force and compliance necessary for proper head slider operation. As the disk in the storage device rotates beneath the bead slider and head suspension, the air above the disk also rotates, thus creating an air bearing which acts with an aerodynamic design of the head slider to create a lift force on the head slider. The lift force is counteracted by a spring force of the head suspension, thus positioning the head slider at a desired height and alignment above the disk which is referred to as the "fly height."
Head suspensions for rigid disk drives include a load beam and a flexure. The load beam includes a mounting region at its proximal end for mounting the head suspension to an actuator of the disk drive, a rigid region, and a spring region between the mounting region and the rigid region for providing a spring force to counteract the aerodynamic lift force generated on the head slider during the drive operation as described above. The flexure includes a gimbal region having a slider mounting surface where the head slider is mounted. The gimbal region is resiliently moveable with respect to the remainder of the flexure in response to the aerodynamic forces generated by the air bearing. The gimbal region permits the head slider to move in pitch and roll directions and to follow disk surface fluctuations.
In one type of head suspension the flexure is formed as a separate piece having a load beam mounting region which is rigidly mounted to the distal end of the load beam using conventional methods such as spot welds. Head suspensions of this type typically include a load point dimple formed in either the load beam or the gimbal region of the flexure. The load point dimple transfers portions of the load generated by the spring region of the load beam to the flexure, provides clearance between the flexure and the load beam, and serves as a point about which the head slider can gimbal in pitch and roll directions to follow fluctuations in the disk surface.
As disk drives are designed having smaller disks, closer spacing, and increased storage densities, smaller and thinner head suspensions are required. These smaller and thinner head suspensions are susceptible to damage if the disk drive is subjected to a shock load or if the suspension experiences excessive pitch and roll motion. Moreover, as the use of portable personal computers increases, it is more likely that head suspensions in these portable computers will be subjected to shock loads. Thus, it is becoming increasingly important to design the head suspension so that it is less susceptible to excessive movements caused by shock loads and by pitch and roll motion, while still maintaining the necessary freedom of movement in the pitch and roll directions. In this manner, damaging contact between the head slider and the disk surface and permanent deformation of components of the head suspension can be prevented.
Mechanisms have been developed for limiting the movement of a free end of a cantilever portion of a flexure for protection against damage under shock loads. One such mechanism is disclosed in U.S. Pat. No. 4,724,500 to Dalziel. The Dalziel reference describes a limiter structure comprising a head slider having raised shoulders to which one or more elements are secured. The elements on the head slider overlap at least a portion of a top surface of the load beam to which the flexure is attached. The structure shown in Dalziel is rather complicated in that an assembly of components is required, including a modified head slider having raised shoulders and limiter elements. These structures add to the weight, height and difficulty of manufacture and assembly of the head suspension. The added structure would be particularly undesirable in the design of smaller head suspension.
Another motion limiter is disclosed in U.S. Pat. No. 5,333,085 to Prentice et al. The head suspension shown in Prentice includes a tab that extends from a free end of a cantilever portion of a flexure. The tab is fitted through an opening of the load beam to oppose the top surface of the load beam (i.e., the surface opposite the side of the load beam to which the flexure is mounted). Although the mechanism shown in the Prentice patent does not significantly change the weight or height of the overall suspension assembly, it does require special manufacturing and assembly steps. To assemble the flexure to the load beam, the tab would likely first be moved through the opening in the load beam and then the flexure would likely be longitudinally shifted relative to the load beam to its mounting position. This interleaving of the flexure and load beam prior to their attachment adds time and complexity to the manufacturing process. Moreover, the tab formation comprises multiple bends, the degree of each bend being important in the definition of the spacing between the tab and the top surface of the load beam. In the design shown in Prentice, errors in the formation of even one bend, including manufacturing tolerances, may affect the ultimate spacing of the limiter mechanism.
Another motion limiter is disclosed in U.S. Pat. No. 5,526,205 to Aoyagi et al. The Aoyagi reference discloses a head suspension having a perpendicular hook at an end of a flexure. The hook is shaped to engage a transverse appendage at the distal end of a load beam to prevent the end of the flexure from displacing vertically too great a distance from the load beam. Such a limiter mechanism, however, does not take into account the dynamic performance of the flexure, including excessive pitch and roll motions that can cause permanent deformation of head suspension components, but instead only limits vertical flexure motion caused by a shock load. In addition, because the single hook engages a transverse appendage on the load beam, the limiter mechanism may induce a roll bias when performing its limiting function.
Yet another motion limiter is disclosed in U.S. Pat. No. 5,877,920 to Resh. The Resh reference discloses a head suspension assembly including a load beam, a recording head and a gimbal. The gimbal is attached to the load beam on the back side opposite the recording head and includes a head mounting tab on which the recording head is mounted. A displacement limiter extends between the load beam and the gimbal for limiting vertical displacement of the gimbal in a direction toward the recording head relative to the load beam. The displacement limiter is disclosed as two tabs formed at the recording head end of the suspension. The tabs are outwardly extending from the load beam in a direction transverse to the longitudinal axis, or are inwardly extending tabs formed on the gimbal, either in a transverse or longitudinal direction. Although the combination of gimbal placement on the backside of the load beam with the formed tabs as motion limiters eliminates the interleaving problem of many types of limiter mechanisms, this type of motion limiter creates other manufacturing problems when forming the head mounting tab and the limiters. In addition, this type of limiting mechanism fails to address the issue of suspension pitch and roll torque during head lift and shock conditions.
In view of the shortcomings described above, a need exists for an improved flexure limiter in a head suspension. A limiter mechanism that provides for a full range of gimballing movement for a head slider mounted on a flexure while also preventing the flexure from being pulled away from the load point dimple of the head suspension is particularly desirable.